Composite bearing materials comprising a hard metal backing strip, such as steel, having a bearing lining composed of copper-lead or leaded bronze are in widespread use for the fabrication of various bearing components for internal combustion engines, vehicle suspension, transmission assemblies and the like. A prior art process extensively employed for the commercial manufacture of composite copper-lead and leaded bronze bearing materials of the foregoing type is described in U.S. Pat. No. 2,986,464, granted to Lewis et al for "Method for Manufacturing Bearing Materials". In accordance with the process described in the aforementioned United States patent, a layer of metal powder having the desired copper, lead and tin content is applied to one surface of a steel backing strip, whereafter the powder layer is sintered at an elevated temperature and thereafter the strip is cooled and is passed through a roll compaction assembly to effect a reduction in the porosity of the sintered powder layer. Following the roll compaction step, the strip is again heated to an elevated temperature to effect a second sintering operation, whereafter the dual-sintered and compacted strip is quenched in a lead bath maintained at a temperature between about 700.degree. F and 900.degree. F in order to effect a filling of any residual porosity remaining after the cold compaction operation.
The process as described in the aforementioned United States patent, while eminently satisfactory for producing a high quality composite strip material, requires a substantial investment in equipment and a relatively large area of plant space to accommodate the double sintering operation separated by an intervening cooling and cold compaction operation. The foregoing processing sequence was considered necessary in order to produce bimetallic bearing materials having adequate bond strength between the lining and backing strip, and to avoid excessive exudation of lead or so-called lead "sweating" during the compaction operation.
It has now been discovered that bimetallic bearing materials having a copper-lead or leaded bronze lining bonded to a steel backing strip can be satisfactorily produced in one sintering and hot compaction operation by carefully controlling powder compositions, particle sizes and sintering and compaction temperatures wherein a substantial simplification and savings in plant space and capital equipment is effected.